[EN] Mediterranean river systems are characterised by more diverse fish assemblages and regional ecological
processes compared with the rest of Europe. A data set from Mediterranean France, Iberia and Greece ( 2000
sites) ...[+]

[EN] Mediterranean river systems are characterised by more diverse fish assemblages and regional ecological
processes compared with the rest of Europe. A data set from Mediterranean France, Iberia and Greece ( 2000
sites) was used to describe the characteristics of fish assemblages, explore their responses to anthropogenic disturbance
and analyse the implications for river quality assessment. There was a southwards decline in species
richness per site, but endemicity and proportion of alien species increased. Sites in the eastern Mediterranean had
higher endemicity, lower site richness and lower number of alien species than sites in western Mediterranean
Europe. Assemblage composition differed between Mediterranean sub-regions, but was dominated by three major
fish types: a salmonid fish type common throughout the study area and two cyprinid-dominated fish types (in some
sub-regions, Salmo trutta L. is present but not numerically dominant), corresponding to a gradient in hydrological
and temperature regimes. Metric responses to perturbation were compared with those found at the European
(larger scale) and basin (smaller scale) levels. Overall metric response was weaker in this Mediterranean application.
The best responses to human pressure were usually obtained with abundance-based metrics and included
the contribution of naturalised alien species. Some widespread alien species contributed to the response to
anthropogenic alteration (notably Cyprinus carpio L. and Lepomis gibbosus (L.)).[-]